Despite fears of an exodus in the wake of a Supreme Court ruling that government workers cannot be required to contribute to labor unions, Hawaii’s government workers have largely maintained their memberships in public sector unions.

However, there could be legal challenges ahead to a recently passed, union-backed state law that only allows them to opt out of membership during a narrow window of the year.

There have been no signs of a mass of union resignations, said Tony Gill, a labor attorney for the University of Hawaii Professional Assembly, a union representing UH faculty, during a forum hosted by the Grassroots Institute of Hawaii on Monday. Nor have the unions lost significant funding from the loss of service fees that previously had been charged to nonmembers.

Hawaii always has required public sector workers to opt in to joining a union but it still charged non-union members service fees, which unions argued were justified because under Hawaii law they must represent workers’ interests regardless of whether the workers are members or not.

The Supreme Court’s decision in Janus v. American Federation of State, County and Municipal Employees meant that the unions — and the state, which deducts the fees from worker paychecks — had to quickly stop collecting the service fees from non-union members unless they opted to continue paying them.

This doesn’t appear to have had a significant effect on union revenues. For example, the Hawaii Government Employees Association, the state’s largest public employee union, said that 96 percent of eligible workers remain union members.

Gill said the Janus ruling appears to have galvanized pro-union sentiment in Hawaii — which has the second-highest rate of union membership in the country — as opposed to having weakened it.

“I think that on average the Janus case is slightly more motivating to pro- unionists as an organizing, rallying cry, than it is to the people who want out because those that wanted out were already largely out,” Gill said. Still, he said it’s too early too tell what the long-term effect of the ruling will be on union membership levels.

The ruling has effectively created three classes of public sector workers: union members; non-union members who choose to pay serv­ice fees; and non-paying, non-union members.

The unions worried that the Janus ruling would effectively create “free riders,” workers who don’t pay dues but still benefit from collective bargaining, contract enforcement and other union benefits. Gill said that, although untested, he didn’t think the unions could be compelled to represent the interests of non-union members who don’t pay service fees.

While Hawaii has quickly complied with the Janus ruling, there could be more legal challenges ahead. Two months before the Janus ruling, Gov. David Ige signed into law Act 7, which says employees who want to opt out of paying union dues can only do so 30 days prior to the initial authorization to deduct dues. Gill said that the law is likely unconstitutional, though he said private agreements between unions and employees would have a better chance of withstanding legal scrutiny.

Jacob Huebert, an attorney who represented Mark Janus in the Supreme Court case and who also spoke during Monday’s event, said that he expected there to be legal challenges to laws like those passed in Hawaii and other states.

“We would argue that it is an unreasonable burden on these workers’ First Amendment rights,” Huebert said. “If you don’t want to be paying money to a union, you should be able to tell them whenever you want to stop those dues from coming out.”